Two people were critically injured in an explosion and fire Tuesday morning after smoking on a catwalk over oil storage tanks in northeast Texas, officials say.

According to Van Zandt County Fire Marshal Chuck Allen, at about 3 a.m. firefighters were called to a fire at an oil storage facility north of Van along state Highway 110.

At the facility are at least six 400-barrel fiberglass storage tanks, three of which caught fire and exploded, NBCDFW reported. Multiple fire departments responded to the scene and ultimately decided to let the fire burn itself out.

A short time later, a 24-year-old man with burns to his face, chest and arms, and a 24-year-old woman also critically injured, showed up at the Van Fire Department seeking medical attention. Both were both taken to the East Texas Medical Center in Tyler before being transferred to Parkland Memorial Hospital in Dallas.

The names of the victims have not been released and neither person has been identified as an employee of the storage facility.

Allen said the victims were believed to be trespassing and smoking on a catwalk above the storage tanks.

Allen added that most of the tanks had very little crude oil in them at the time of the explosion.

The fire marshal is working to identify which company owns the facility.